Buzz Brainteaser

Welcome to Buzz Brainteaser, the trivia feature on BuzzSugar! Every weekday I'll test your knowledge about TV shows, music and movies. If you enter in the correct answer, you win points!
On a Halloween episode of 90210, the gang is at a costume party: Brenda and Dylan dress as Bonnie and Clyde, Steve goes as Zorro and Kelly dresses as a sexy witch.
What does Donna go as?